Method of making precursor hollow castings for tube manufacture

ABSTRACT

A tubular formation technique utilizing centrifugal casting incorporating a moveable launder system to deliver molten alloy along an extended length within a centrifugal caster to form a hollow tubular precursor of extended length. The technique is adaptable to all alloy systems but may be particularly suited for so called “hard alloys” that are susceptible to substantial work hardening or are difficult to extrude.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of and priority from U.S. ProvisionalApplication 60/862,056 filed Oct. 19, 2006 the contents of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to the field of hollow tubemanufacture and more particularly to the field of centrifugal casting ofelongate hollow tube precursors adaptable for flow forming or othertreatments.

BACKGROUND OF THE INVENTION

It is well known to form tubes from materials such as aluminum andmagnesium using extrusion techniques or seam welding rolled sheet stock.Tubes of such materials may also be formed by drawing a hollow blankover a mandrel or flow forming an extrusion formed precursor over amandrel. While such techniques for forming tubes may be suitable formany materials, they may be difficult to apply to alloys such as highductility aluminum alloys that exhibit substantial work hardening or tomagnesium alloys that do not exhibit good hot deformation behaviorunless extremely low extrusion speeds are utilized. Alloys that arecharacterized by substantial amounts of work hardening may be desirableto accommodate deformation strain during fabrication of complex shapes,or in the case of magnesium alloys for light weight.

SUMMARY OF THE INVENTION

The present invention provides advantages and alternatives over priorpractices by providing tubular formation techniques that areparticularly suited for so called “hard alloys” that are susceptible tosubstantial work hardening or are difficult to extrude.

According to one aspect, a process is provided utilizing centrifugalcasting incorporating a moveable launder system to deliver molten alloyalong an extended length within a centrifugal caster to form a hollowtubular precursor of extended length.

According to another aspect, a process is provided utilizing centrifugalcasting incorporating a moveable launder system to deliver layers ofalloy and/or composite material along an extended length within acentrifugal caster to form a hollow tubular precursor of extendedlength.

According to still another aspect, a process is provided wherein acentrifugal caster incorporating a moveable launder system deliveringmolten alloy along an extended length within the caster is mated with aflow forming procedure to yield a tube of desired thickness formed froma work hardenable alloy or from alloys that are difficult to hot work bystandard methods like extrusion.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings which are incorporated in and which constitute apart of this specification illustrate exemplary practices in accordancewith the present invention and, together with the general descriptionabove and the detailed description set forth below, serve to explain theprincipals of the invention wherein:

FIG. 1 is a view illustrating a casting system incorporating aretractable elongate launder in inserted relation within a centrifugalcaster;

FIG. 2 is a view similar to FIG. 1 with the launder retracted towardsthe mouth of the caster;

FIG. 3A is a side view of cast billets of tubular construction formed bythe system illustrated in FIGS. 1 and 2;

FIG. 3B is an end view of cast billets of tubular construction formed bythe system illustrated in FIGS. 1 and 2; and

FIG. 4 is a schematic view of a tube flow forming operation that may bepaired with a casting system as illustrated in FIGS. 1 and 2.

While embodiments of the invention have been illustrated and generallydescribed above and will hereinafter be described in connection withcertain potentially preferred procedures and practices, it is to beunderstood and appreciated that in no event is the invention to belimited to such embodiments and procedures as may be illustrated anddescribed herein. On the contrary, it is intended that coverage shallextend to all alternatives and modifications as may embrace the broadprincipals of the invention within the true spirit and scope thereof.

DETAILED DESCRIPTION

Reference will now be made to the various drawings wherein like elementsare designated by like reference numerals throughout the various views.As illustrated, in accordance with the present invention a centrifugalcaster 10 is mated with a moveable launder 20. The launder 20 preferablyincludes a proximal reservoir portion 22 for acceptance of a moltenalloy and a distal insertion portion 24 of reduced hemispherical crosssection for insertion an extended length into the caster 10.

As shown, the launder 20 may be mounted on a carriage assembly 30 forreciprocating movement in axial relation to the caster 10. While thecarriage assembly 30 is illustrated as a cart mounted on rails, it islikewise contemplated that virtually any supporting structure adapted totranslate reciprocal movement to the launder may be used.

In operation the insertion portion 24 of the launder 20 may be projectedthrough a mouth opening of the caster 10 a predetermined length alongthe interior of the caster. While the insertion portion 24 is within thecaster 10, a molten alloy may be delivered to the reservoir portion 22thereby causing the alloy to flow along the insertion portion fordeposit at the interior of the caster 10. As will be appreciated, themoveable nature of the launder 20 permits the location of alloy depositto be moved inwardly away from the mouth of the caster. Moreover, thealloy can be deposited progressively along the length of the caster 10by inserting or withdrawing the insertion portion 24 while the alloy isbeing delivered. Moreover, by use of controlled reciprocation, layers ofsimilar or dissimilar material may be deposited at the interior of thecaster 10 so as to form layers within the final cast billets. While theprocess may be used with substantially any metal system, it iscontemplated that the system may be particularly useful for aluminum,aluminum alloys, magnesium, magnesium alloys, titanium and titaniumalloys, copper and copper alloys, and refractory metals and theiralloys.

By use of the reciprocating launder system it has been found that it maybe possible to increase the thickness of billets formed within thecaster 10 and/or to cast alloys that may not be suitable for centrifugalcasting or for casting into standard extrusion billets. By way ofexample only, it has been found that tubes of high ductility aluminumalloys may be formed with substantial wall thickness on the order ofabout 10 mm or greater. Benefits are also believed to be applicable toalloys of materials such as magnesium and titanium that arecharacterized by limited extrudability.

It is also contemplated that billets cast using the reciprocatinglaunder system may be more amenable to subsequent tubular flow formingresulting in a lengthened and thinned structure. By way of example onlyand not limitation, a representative flow forming process is illustratedin FIG. 4. As shown, in this process a centrifugal casting 50 engages achuck 52 with a support tool 54 held at the interior of the casting 50.As the casting 50 is rotated, and the support tool 54 may or may not berotated, the casting 50 engages a spinning forming tool 56 which causesthe walls of the casting to be thinned and elongated.

It is to be understood that while the present invention has beenillustrated and described in relation to potentially preferredembodiments, constructions, and procedures, that such embodiments,constructions, and procedures are illustrative only and that theinvention is in no event to be limited thereto. Rather, it iscontemplated that modifications and variations embodying the principalsof the invention will no doubt occur to those of skill in the art. It istherefore contemplated and intended that the present invention shallextend to all such modifications and variations as may incorporate thebroad aspects of the invention within the true spirit and scope thereof.

1. A casting system comprising: a centrifugal caster having an interiorand a material acceptance opening; and an elongate moveable launderadapted for insertion through the material acceptance opening and intothe interior of the caster for delivery of molten metal to positionsalong the interior of the caster spaced away from the materialacceptance opening.
 2. The casting system of claim 1, wherein theelongate moveable launder is moveable in reciprocating relation relativeto the caster.
 3. The casting system of claim 2, wherein the elongatemoveable launder is mounted on rails.
 4. The casting system of claim 1,wherein the molten metal is selected from at least one of the groupconsisting of: aluminum, aluminum alloys, magnesium, magnesium alloys,titanium and titanium alloys, copper and copper alloys, and refractorymetals and their alloys.
 5. Billets formed by the casting system ofclaim
 1. 6. The casting system of claim 1, further comprising a flowforming apparatus adapted to process billets from the caster.
 7. Amethod of centrifugally casting a tubular billet, the method comprisingthe steps of: providing a centrifugal caster having an interior and amaterial acceptance opening; providing an elongate moveable launderadapted for reciprocating insertion and withdrawal through the materialacceptance opening and into the interior of the caster for delivery ofmolten metal to positions along the interior of the caster spaced awayfrom the material acceptance opening; inserting a distal portion of thelaunder into the interior of the caster; delivering a quantity of moltenmetal along the launder from a position outside the caster to theinterior of the caster for deposit at locations spaced away from thematerial acceptance opening; and expelling hollow substantially tubularbillets from the caster.
 8. The method as recited in claim 7, whereinthe molten metal is deposited as the launder is moved in reciprocatingrelation to the caster such that the molten metal is deposited in layersalong the length of the caster, and where the individual layers can be adifferent metal or alloy.
 9. The method as recited in claim 7, whereinthe elongate moveable launder is mounted on rails.
 10. The method asrecited in claim 7, wherein the molten metal is selected from at leastone of the group consisting of: aluminum, aluminum alloys, magnesium,magnesium alloys, titanium and titanium alloys, copper and copperalloys, and refractory metals and their alloys.
 11. A method ofcentrifugally casting and flow forming a tubular billet, the methodcomprising the steps of: providing a centrifugal caster having aninterior and a material acceptance opening; providing an elongatemoveable launder adapted for reciprocating insertion and withdrawalthrough the material acceptance opening and into the interior of thecaster for delivery of molten metal to positions along the interior ofthe caster spaced away from the material acceptance opening; inserting adistal portion of the launder into the interior of the caster;delivering a quantity of molten metal along the launder from a positionoutside the caster to the interior of the caster for deposit atlocations spaced away from the material acceptance opening; expellinghollow substantially tubular billets from the caster; and delivering thetubular billets to a wall thinning flow forming apparatus adapted toprocess the billets from the caster.
 12. The method as recited in claim11, wherein the molten metal is deposited as the launder is moved inreciprocating relation to the caster such that the molten metal isdeposited in layers along the length of the caster, and where theindividual layers can be a different metal or alloy.
 13. The method asrecited in claim 11, wherein the elongate moveable launder is mounted onrails.
 14. The method as recited in claim 11, wherein the molten metalis selected from at least one of the group consisting of: aluminum,aluminum alloys, magnesium, magnesium alloys, titanium and titaniumalloys, copper and copper alloys, and refractory metals and theiralloys.